|
| 1 | +package composite |
| 2 | + |
| 3 | +import ( |
| 4 | + "errors" |
| 5 | + "fmt" |
| 6 | + "io" |
| 7 | + "io/fs" |
| 8 | + "net/url" |
| 9 | + "sort" |
| 10 | + |
| 11 | + "golang.org/x/exp/maps" |
| 12 | +) |
| 13 | + |
| 14 | +type FS interface { |
| 15 | + fs.ReadFileFS |
| 16 | + |
| 17 | + // Mount mounts a filesystem to the given mount point. |
| 18 | + // The mount point is the scheme of the URI. |
| 19 | + Mount(mountPoint string, fs fs.FS) |
| 20 | + // ListMounts returns a list of all mount points in sorted order. |
| 21 | + ListMounts() []string |
| 22 | +} |
| 23 | + |
| 24 | +type vfs struct { |
| 25 | + mounted map[string]fs.FS |
| 26 | +} |
| 27 | + |
| 28 | +var ( |
| 29 | + _ fs.FS = (*vfs)(nil) |
| 30 | + _ fs.ReadFileFS = (*vfs)(nil) |
| 31 | +) |
| 32 | + |
| 33 | +func NewFS() FS { |
| 34 | + return &vfs{mounted: make(map[string]fs.FS)} |
| 35 | +} |
| 36 | + |
| 37 | +func (f *vfs) Open(name string) (fs.File, error) { |
| 38 | + uri, err := f.validatePath(name) |
| 39 | + if err != nil { |
| 40 | + return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrInvalid} |
| 41 | + } |
| 42 | + |
| 43 | + vfs, err := f.resolve(uri) |
| 44 | + if err != nil { |
| 45 | + return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist} |
| 46 | + } |
| 47 | + return vfs.Open(name) |
| 48 | +} |
| 49 | + |
| 50 | +func (f *vfs) ReadFile(name string) ([]byte, error) { |
| 51 | + uri, err := f.validatePath(name) |
| 52 | + if err != nil { |
| 53 | + return nil, &fs.PathError{Op: "readfile", Path: name, Err: fs.ErrInvalid} |
| 54 | + } |
| 55 | + |
| 56 | + vfs, err := f.resolve(uri) |
| 57 | + if err != nil { |
| 58 | + return nil, &fs.PathError{Op: "readfile", Path: name, Err: fs.ErrNotExist} |
| 59 | + } |
| 60 | + |
| 61 | + if vfs, ok := vfs.(fs.ReadFileFS); ok { |
| 62 | + content, err := vfs.ReadFile(name) |
| 63 | + if err != nil { |
| 64 | + return nil, &fs.PathError{Op: "readfile", Path: name, Err: getUnderlyingError(err)} |
| 65 | + } |
| 66 | + |
| 67 | + return content, nil |
| 68 | + } |
| 69 | + |
| 70 | + file, err := vfs.Open(name) |
| 71 | + if err != nil { |
| 72 | + return nil, &fs.PathError{Op: "readfile", Path: name, Err: getUnderlyingError(err)} |
| 73 | + } |
| 74 | + defer file.Close() |
| 75 | + |
| 76 | + content, err := io.ReadAll(file) |
| 77 | + if err != nil { |
| 78 | + return nil, &fs.PathError{Op: "readfile", Path: name, Err: getUnderlyingError(err)} |
| 79 | + } |
| 80 | + |
| 81 | + return content, nil |
| 82 | +} |
| 83 | + |
| 84 | +func (f *vfs) Mount(mountPoint string, fs fs.FS) { |
| 85 | + f.mounted[mountPoint] = fs |
| 86 | +} |
| 87 | + |
| 88 | +func (f *vfs) ListMounts() []string { |
| 89 | + mounts := maps.Keys(f.mounted) |
| 90 | + sort.Strings(mounts) |
| 91 | + |
| 92 | + return mounts |
| 93 | +} |
| 94 | + |
| 95 | +// validatePath checks if the provided path is a valid URL and returns its URI. |
| 96 | +func (f *vfs) validatePath(name string) (*url.URL, error) { |
| 97 | + uri, err := url.Parse(name) |
| 98 | + if err != nil { |
| 99 | + return nil, err |
| 100 | + } |
| 101 | + if uri.Scheme == "" { |
| 102 | + return nil, fmt.Errorf("missing scheme in path: %s", name) |
| 103 | + } |
| 104 | + return uri, nil |
| 105 | +} |
| 106 | + |
| 107 | +// resolve returns the filesystem mounted at the given URI scheme. |
| 108 | +func (f *vfs) resolve(uri *url.URL) (fs.FS, error) { |
| 109 | + vfs, ok := f.mounted[uri.Scheme] |
| 110 | + if !ok { |
| 111 | + return nil, fmt.Errorf("no filesystem mounted at: %s", uri.Scheme) |
| 112 | + } |
| 113 | + return vfs, nil |
| 114 | +} |
| 115 | + |
| 116 | +// getUnderlyingError returns the underlying error of a path error. |
| 117 | +// If it's not a path error it returns the error itself. |
| 118 | +func getUnderlyingError(err error) error { |
| 119 | + var pathErr *fs.PathError |
| 120 | + if errors.As(err, &pathErr) { |
| 121 | + return pathErr.Err |
| 122 | + } |
| 123 | + return err |
| 124 | +} |
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